California Department of Transportation (Caltrans) – Green Technologies for Reducing Slope Erosion
The California Department of Transportation (Caltrans) Division of Research and Innovation conducted a Preliminary Investigation (PI) to identify strategies for reducing roadside slope erosion and preventing costly slope failures as climate change alters patterns of precipitation in California. The PI found that in general, California is a leader in erosion control and stormwater management, but recommended follow-up research on the effectiveness of specific plants or “green” products that may enhance or improve the nature-based methods for stabilizing slopes that California has already begun to implement.
The PI found that California is a leader in both research and implementation of innovative erosion technologies. Caltrans has developed an Erosion Control Toolbox, which is an online compilation of resources for erosion control, including standards, guidance, and best management practices for Caltrans Landscape Architects. Caltrans has also conducted several soil stabilization studies to assess different soil stabilization methods and to develop guidance. These studies include:
- a vegetation establishment and maintenance study that will be used to develop vegetation establishment guidelines for plant species for both short-term stabilization and long-term cover;
- a roadside vegetated treatment study that monitored eight test sites to study pollution removal in biofiltration strips (i.e., sloped areas adjacent to impervious surfaces, planted with vegetation to filter pollutants from runoff); and
- a statewide erosion control review to assess the effectiveness of current erosion control practices used by Caltrans.
The PI highlights the innovative work of several other states in researching and implementing a variety of bioengineering methods for controlling erosion - techniques that combine vegetation with mechanical construction. The Texas Department of Transportation is a leader in utilizing compost for erosion management on slopes, which improves the quality of the soil and reduces the quantity of waste introduced into the watershed. Washington State Department of Transportation has integrated soil bioengineering into its roadside material specifications, and often combines bioengineering with geotechnically engineered solutions for restoring degraded slopes. The Stormwater Management Academy at the University of Central Florida has created a detailed guidance manual for making grass seed more resistant to being washed away by water flow prior to germination (called polymer-enhanced bioengineering techniques).
The PI lists national guidance from AASHTO, including Design Guidance for Stormwater and Erosion & Sedimentation Control, a compilation of best management practices manuals. In addition to listing both federally-sponsored and state-sponsored best management practices manuals and guidance, this guidance also includes an online BMP Manual Builder to assist states and municipalities in creating their own stormwater treatment practice design manuals. The PI also lists related research by several different state DOTs and other researchers, and additional resources for vegetative or bioengineering approaches to slope erosion control.
In November 2010, Caltrans issued a Technical Guide for sustainable erosion control that presents considerations for soil, water, and vegetation in designing erosion control projects. Although the PI highlighted altered precipitation due to climate change as a concern for erosion control, the 2010 Technical Guide directs users to the Western Regional Climate Center for data on the amount and intensity of local annual rainfall, but does not include consideration of climate-related changes in precipitation.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on December 29, 2014.
Publication Date: January 28, 2010
- California Department of Transportation (Caltrans)
- Best practice